There is conventionally known a valve timing controller which includes a housing receiving a drive force of a crankshaft for an engine and a vane rotor which is accommodated in the housing to transmit the drive force of the crankshaft to a camshaft, where the vane rotor is relatively rotated in a retard side or an advance side to the housing by pressure of an operating fluid in a retard chamber or an advance chamber, controlling a phase of the camshaft relative to the crankshaft, i.e., valve timing (for example, refer to US-2005/0284433 A1).
In such a valve timing controller, a torque fluctuation the camshaft receives from an intake valve or an exhaust valve when the intake valve or the exhaust valve is driven for opening/closing is transmitted to the vane rotor. As a result, the vane rotor is subject to the torque fluctuation to the retard side or the advance side relative to the housing.
In a case of supplying an operating fluid to the advance chamber to change a phase of the camshaft relative to the crankshaft from the retard side to a target phase of the advance side, the operating fluid in the advance chamber receives force in such a manner as to be flown out from the advance chamber, caused by that the vane rotor is subject to the torque fluctuation to the retard side. As a result, the vane rotor moves back to the retard side by the torque fluctuation as shown in a broken line of FIG. 20, increasing a response time until the vane rotor reaches the target phase. This phenomenon is significant when the pressure of the operating fluid from a fluid supply source is low.
Therefore, it is considered that a one-way valve is disposed in a supply passage for supplying the operating fluid to the advance chamber, preventing the operating fluid from flowing out from the advance chamber even if the vane rotor is subject to the torque fluctuation. As a result, it is known that this, as shown in a solid line of FIG. 20, prevents the vane rotor from returning back to a direction opposite to the target phase with respect to the housing during phase controlling, enhancing responsiveness of the phase control.
However, at the time of holding the vane rotor at the target phase, the operating fluid in the retard chamber is discharged from the retard chamber, caused by that the vane rotor receives the torque fluctuation to the advance side, so that the vane rotor tends to relatively rotate in the advance side to the housing. As a result, particularly when the supply pressure is low, the valve timing is more likely to be shifted to the advance side.
In view of the above, there exists a need for a valve timing controller which overcomes the above mentioned problems in the conventional art. The present invention addresses this need in the conventional art as well as other needs, which will become apparent to those skilled in the art from this disclosure.